Furnace control device



Oct. z8, 1952 Filed Oct. 2. 1950 F. HARBIN, JR

FURNACE CONTROL DEVICE 2 SHEETS-SHEET l.

Fem

4'FRANK HARMN, JP..

)www M r Avvomsvs Oct. 28, 1952 F. HARBIN, JR 2,615,534

l FURNACE CONTROL DEVICE Filed oct. 2. 195o 2 SHEETS-Smm 2 Room 5nveuron F1a. YKANK HAnsm., Jn.

s (xiv-Maf (hm-MW Patented ct. 28, 1952 Frank Harbin, Jr., Holland,Mich.,fja'ssign'or to Home Furnace`Company, Holland, Mich., a cor-'poration 'of Michigan Application'October 2, 1950, Serial No. 187,863

2 Claims. 1

This invention relates to furnace-ccntrols and more particularly to thecontrols for warm air furnaces used `to heat residences. It is adaptedto be applied to furnaces having different tyrxes of yburners such asgas or fuel oil and Ait maybe usedwith the so-called gravity ow type offurnace in which the ow of air from the furnace to the room is caused bygravity or it may be used With the forced air circulation vtype offurnace in which a fan is used to induce thecirculation.

The object-of the device is to cause a more constant circulationof airfrom the furnace into y'the room so that the v-air in the room will notlong remain motionless and stagnant.

To accomplish this result in a gravity flow furnace the furnace isprevented from becoming cold after the room temperature has reached thede'- sired normal degree which is variable but which may be arbitrarilyset for the purpose of this -description at 70. After'the roomtemperature has reached the normal 70 the burner of the yfurnace iscontrolled to maintain it at moderate ywarmth so that it will induce thevgravity lflow of -air into the room and this moderate vwarmth of thefurnace, which maybe arbitrarily `stated as 100, is maintained until theroom 'temperature has risen slightly above the Anormal 70 to atemperature which We may state as '71 and at this point the furnaceburner stops operation until .the room temperature drops below '71 whenythe A'furnace burner will again operate to raise the furnacetemperature to 100". And when the room temperature drops belowgthenormal 70 the furnace will gc into full operation raising itstemperatureconsiderably above 100 to raise the room temperature to normal.

In a forced aircirculation system using a fan to-circulate the air thesame control of the burner is usedas above explained for the gravitysystem but in this forced air circulation a two speed fan may be usedand Vthe operation of the fan lis controlled so that when the roomtemperature is below 70" the fan operates at high` speed but when the.temperature reaches and rises above the normal 70 the fan will beautomatically controlled to operate at lowspeed and this low speedoperation of the Ifan continues at all room temperatures above 70 untilthey furnace temperature drops to or below substantially roomtemperature.

.For amore complete and detailed understanding of the inventionreference is made to the accompanying drawings, in which,

Fig. l1 vis a diagram illustrating the electrical connections andvarious `instruments which may be used in a forced circulation system.

Fig. J2 `is -a like diagram of the device adapted fora gravity owsystem. l

Fig. 3 is a sectional view on the line "3-1 ol' Fig. 5 illustrating thethermostatic switch deviceI controlled'by the furnace Yjackettemperature' 'and adapted for the forced circulation system of Fig. 1.

Eig. 4 is a like section on the line v3-4 f Fig. 5 showing Athe jackettemperature controlledthermostatic switch adapted for the gravity flo'wsystem of Fig. 2'.

Fig. 5 is an elevation of the thermostatic device used in the furnacejacket, its mechanism being' that of ither'lig or'Fig. 4, and c Fig. 6is a diagrammatic illustration f Jthe' room thermostat used vin eitherthe forced circulation or gravity flow system.

yLike reference numbers refer to 'like ,parts in all of the-gures-Referring now to Fig. 'v2' which is a dag'ramof the gravity 4circulationsystem in which the air will not circulate through the' heatings'ystemand into the `room to any extent, unless the 'fur'- nace temperature is.higher .than the room teper'ature. The furnace burner is controlled an.electrically operated fuel valve `'l whichp'referably isfopened whenenergizedl and closed when de-energi'zed. yThe burner isv of the singlelStage type, that is, it has only one stage of operation. It is either'full on or off. A room thermostat generally indicated as 2 is locatedlin rthe rooin and it is provided with independently adjustableelctricalcontacts 3 and '4. IThe circuitis opened or closed through thesecontacts by a thermostatically operated contact member 5. The contactmember r5 is herein illustrated as a single member but it may consist oftwo separate Contact members although it is preferable that whether thecontact member be single or double .itshalll be operated vby a singlethermostatic element Aly which is herein shown as a coiledbimetal-strip. however different thermostatic elements -may -besubstituted for that shown. The device is-.adjustedso that circuit is.broken at the contact v-3 when theroom temperature reaches normalfsuchas .70 and `the circuit is broken at the contact-V when .the roomAtemperature has lrisen slightly above normal, such as 71. Itis to be-understood that these temperatures are given as arbitrary examples and.may be altered by adjustment-of the thermostat.

` The furnace jacket 'l is provided with the jacket thermostat 8A whichmay be of any Vconventional construction. That herein shown comprises ashaft Sprojectingin'to the furnace jacket and Shaving coiled about it abimetal strip l0 3 which is connected to the shaft 9 at one end and tothe fixed body of the thermostat at the other end, Changes oftemperature in the furnace jacket will affect the thermostatic element lto cause slight rotation of the shaft 9.

The jacket thermostat is provided with a head which for this gravitysystem contains two switches l2 and I3 as illustrated in Fig. 4. Theseswitches are operated to open or close their respective circuits by cams|4 and I5 each adjustably mounted upon a disk I6 attached to the shaft 9and oscillated thereby in either direction with changes of temperaturein the furnace jacket. The cam I4 which actuates the switch |2 isadjusted to break its circuit when the jacket temperature reaches a highlimit such as 250. The cam |4 is of such design that it will not breakthe circuit at the switch |2 at any low jacket temperature. The cam Iwhich actuates the switch I3 is adjusted to break its circuit when thejacket temperature reaches a moderate temperature, such as 100, which issufliciently higher than the room temperature to maintain the gravityair fiow. This switch I3 is likewise closed at all temperatures below100.

Electric current to operate the fuel valve I and controlled by thevarious switches is supplied by a transformer |'I which is supplied bycurrent from a conventional source through the conductors I8. Aconductor IS connects the room thermostat contact 3 with the jacketthermostat switch I 2 and the conductor 20 connects the room thermostatcontact 4 with the jacket thermostat switch I3. Both of the jacketswitches I2 and I3 are connected to the fuel valve by the conductor 2|and the conductor 22 leads from the fuel valve through the transformerI'I to the contact breaker 5 of the room thermostat.

Now when the room temperature is below 70 and the furnace jackettemperature is below 100 all of the switches will be closed and the fuelvalve will be energized and opened so that the re will burn to heat thefurnace. As the jacket temperature increases and rises above 100 theswitch I3 will be opened but inasmuch as this controls only one of thecircuits to the fuel valve it will not by itself stop operation of theburner. When the room temperature reaches 70 the current through theconductor I9 will be broken at the Contact 3 which will open the othercircuit to the fuel valve de-energizing it and causing it to close andcease burning of the furnace.

Under the foregoing conditions the jacket temperature may beconsiderably above 100 and although the furnace is not operating it issufficiently warm to cause circulation of air into the room. As thefurnace gradually cools and the jacket temperature drops below 100, ifthe room temperature is not above 71, the switch I3 will be closed andas the circuit is still maintained through the contact 4 and the fuelvalve will again open and cause operation of the furnace, thusmaintaining the jacket temperature at substantially 100 unless the roomtemperature rises above 71 at which point the circuit through theconductor 20 will be broken at the contact 4 and even with the switch I3closed the fuel valve cannot become energized.

By the foregoing means and as long as the room temperature is above 70the furnace will be kept sufficiently warm to cause air circulationunless the room temperature rises above 71 and then the furnace becomescompletely inoperative. When the room temperature drops below 70 bothconductors |9 and 20 will be closed at the 4 contacts 3 and 4 and fulloperations of the furnace will begin.

Referring to Fig. 1 which is a diagram of the forced air circulationsystem, the furnace is provided with the same type of fuel valve I andthe same type of room thermostat 2 is used in the room. In addition afan 25 is provided in the air circulatory system. The same type offurnace jacket thermostat is provided in this system excepting that itis provided with a third switch 26 which controls operation of the fan.A third adjustable cam 21 is mounted on the disk |6 which operates thefan switch 26. This arrangement is illustrated in Fig. 3.

The fan may be driven by a two speed electric motor 25. It is customaryto operate the fan motor on high voltage current such as 11C-volt andthe fuel valve is preferably operated by a lower voltage current such as25-vo1t. For that reason the motor is connected directly into the11G-volt system and the lower voltage for the fuel valve system isprovided by the like transformers 28 two of which are shown but all ofthe low voltage current may be supplied by one transformer if desired.This system also includes a relay switch generally indicated as 29provided with two switch levers 30 and 3| simultaneously actuated by amagnet 32. These switch levers 30 and 3| are moved to the solid lineposition when the magnet 32 is energized and dropped to the dotted lineposition when the magnet is de-energized. The relay includes thecontacts 33 and 34 which coact with the arm 30 and the contacts 35 and36 which coact with the arm 3|.

The high voltage current is carried by the conductors 40 and 4I,conductor 4| being connected directly to the ground post of the twospeed fan motor 25. The conductor 40 is joined with the fan switch 26 bythe conductor 42 and the conductor 43 leads from the switch 26 to therelay switch lever 3|. The conductor 44 leads from the relay contact 35to the high speed post of the motor 25 and the relay contact 36 isconnected by the conductor 45 with the low speed post of the motor 25.By this means the fan motor is operated at high speed when the magnet 32is energized and the arm 3| lifted and the fan motor is operated at lowspeed when the magnet is de-energized and the lever 3| is lowered aslong as fan switch 26 is in contact.

The conductors 46, 41 and 48 form a circuit for the magnet 32 throughthe transformer 28 and the room thermostat contact 3 and the thermostatmember 5 thereof when the room temperature is below 70. When the magnet32 is energized the relay lever 30 is raised into engagement with thecontact 33 and circuit to the fuel valve is completed through theconduit 50, the jacket thermostat switch I2, and the conduits 5|, 52 and53 through the transformer 28. When the room temperature rises above 70,but is below 71, the relay magnet 32 is de-energized and the lever 30drops against the contact 34 and if the furnace jacket temperature isbelow the fuel valve is energized through the conductor 50, the jacketthermostat switch |3, the conduit 55, through the room thermostat, theconduit 48, the jumper 56, and the conduits 52 and 53.

Therefore in this forced air circulation when the room temperature isbelow 7 0 the fuel valve is open so that the furnace is in fulloperation and the fan motor is operated at high speed. But when the roomtemperature reaches the normal 70 the circuit is broken at the contact 3in the room thermostat and the relay magnet is cie-energized. The relaylevers then drop and close the circuits to operate the fan motor at lowspeed and if the furnace jacket temperature is above 100 the circuit tothe fuel valve is broken by the jacket thermostat switch I3. 1f thejacket temperature drops below 100 while the room temperature is below71 the jacket switch I3 will close and open the fuel valve to raise thefurnace temperature. However when the room, temperature rises above 71othe circuit is broken at the contact l and the fuel valve will not openno matter how low the furnace temperature drops and if the furnacetemperature falls below substantially room temperature the jacketthermostat switch 26 will open to stop operation of the fan motor.

Therefore it will be seen that this system, applied to either thegravity flow circulation or the forced air-circulation system, willoperate to raise the room temperature to a normal 70 and will alsomaintain an air circulation through the system at a lower temperatureand reduced flow when the room temperature is above 70 but below 71.When the room temperature rises above 71 the heating system ceasesoperation completely so that the room temperature will not be raised toan undesirable point and at this temperature the lack of air circulationin the room is not noticeable.

The invention is defined in the appended claims and is to be consideredcomprehensive of all forms of structure coming Within their scope.

I claim:

1. The combination with a room heating system having a furnace with anelectrically controlled single stage burner therefor, and a twospeedelectric air circulating fan, of a control device comprising a roomthermostat having two electric contact breakers operated by athermostatic element to open and close at different temperatures, afurnace temperature controlled thermostat having two electric contactbreakers operated by a thermostatic element to open and close atdifferent temperatures to control the operation of the burner, saidfurnace thermostat also having a third contact breaker operated by thesaid thermostatic element to control operation of the fan, a singlerelay switch having two synchronously moving switch members, each makingand breaking two circuits, one of said switch members being in theburner control circuit and the other in the fan control circuit, thelower temperature room thermostat contact breaker controllingenergization of said relay switch which, when energized, closes thecircuit through the higher temperature furnace thermostat circuitbreaker to operate the furnace burner and also closes the high speed fancircuit through the furnace thermostat fan contact breaker, said relayswitch, when deenergized, closes the circuit through the lowertemperature furnace thermostat circuit breaker to operate the furnaceburner, and also closes the low speed fan circuit through the furnacethermostat fan circuit breaker, the higher temperature room thermostatcircuit breaker being in series circuit with the lower temperaturefurnace thermostat circuit breaker.

2. The elements of claim 1 in which deenergization of the relay switchthrows the higher temperature room thermostat circuit breaker and thelower temperature furnace thermostat circuit breaker in series circuitwith the higher temperature furnace thermostat circuit breaker.

FRANK HARBIN, J R.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS

